 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LNK457VG-TL Datasheet(PDF) 8 Page - Power Integrations, Inc. |
|
||||||||||||||||||||||||||||||
LNK457VG-TL Datasheet(HTML) 8 Page - Power Integrations, Inc. |
|
|
8 / 20 page  Rev. A 11/01/10 8 LNK454/456-458/460 www.powerint.com This can be achieved through selecting the appropriate value of output capacitance and the value of the current sense resistor. If the peak of the ripple voltage exceeds 520 mV, the device will enter cycle skipping mode which will reduce PFC performance (lower PF and increase THD). Transformer Considerations for use with Leading Edge TRIAC Dimmers Audible noise can be created in the transformer due to the abrupt change in flux when the TRIAC turns on. This can be minimized by selecting cores with higher mechanical resonant frequencies. Cores with long narrow legs should be avoided (e.g. EEL types). RM and other pot core types are good choices and produce less audible noise than EE cores for the same flux density. Reducing the core flux density (BM) also reduces audible noise generation. A value below 1500 Gauss usually eliminates any noise generation but reduces the power capability of a given core size. Working with TRIAC Dimmers The requirement to provide output dimming with low cost, TRIAC based, leading edge phase dimmers introduces a number of trade-offs in the design. For correct operation incandescent phase angle dimmers typically have a specified minimum load, typically ~40 W for a 230 VAC rated unit. This is to ensure that the current through the internal TRIAC stays above its specified holding current threshold. Due to the much lower power consumed by LED lighting the input current drawn by the lamp is below the holding current of the TRIAC within the dimmer. The input capacitance of the driver allows large inrush currents to flow when the TRIAC fires. This then generates input current ringing with the input stage and line inductance which may cause the current to fall below the TRIAC holding current. Both of these mechanisms cause undesirable behavior such as limited dimming range and/or flickering. To overcome these issues two circuit blocks, damper and bleeder, are incorporated in dimming applications. The drawback of these circuits is increased dissipation and therefore reduced efficiency of the supply. Figure 8 shows the line voltage and current at the input of a leading edge TRIAC dimmer. In this example, the TRIAC conducts at 90 degrees. Figure 9 shows the desired rectified bus voltage and current. Figure 10 shows undesired rectified bus voltage and current with the TRIAC turning off prematurely and restarting. On the first half cycle this is due to the input current ringing below the holding current of the TRIAC, excited by the initial inrush current. The second half cycle also shows the TRIAC turning off due to the current falling below the holding current towards the end of the conduction angle. This difference in behavior on alternate half cycles is often seen due to a difference in the holding current of the TRIAC between the two operating quadrants. If the TRIAC is turning off before the end of the half cycle or rapidly turning on and off then a bleeder and damper circuit are required. In general as power dissipated in the bleeder and damper circuits increases, so does dimmer compatibility. Initially install a bleeder network across the rectified power bus (R10, R11 and C6 in Figure 7) with initial values of 0.1 µF and a total resistance of 1 k W and power rating of 2 W. Figure 8. Ideal Input Voltage and Current Waveforms for a Leading Edge TRIAC Dimmer at 90° Conduction Angle. 50 100 150 200 250 300 350 400 Conduction Angle (°) 350 250 150 50 -50 -150 -250 -350 0.35 0.25 0.15 0.05 -0.05 -0.15 -0.25 -0.35 PI-5983-060810 Voltage Current 0.5 0 50 100 150 200 250 400 350 300 Conduction Angle (°) 350 300 250 200 150 100 50 0 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 PI-5984-060810 Voltage Current Figure 9. Resultant Waveforms Following Rectification of Ideal TRIAC Dimmer Output. 0 50 100 150 200 250 400 350 300 Conduction Angle (°) 350 300 250 200 150 100 50 0 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 PI-5985-102810 Voltage Current Figure 10. Example of Phase Angle Dimmer Showing Erratic Firing. |
Similar Part No. - LNK457VG-TL |
|
Similar Description - LNK457VG-TL |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.NET |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
